1. Field of the Invention
The present invention relates generally to packaging machines and, more particularly, to a vacuum packaging apparatus for use in evacuating the air in an open-ended package and sealing the evacuated package.
2. Discussion of the Prior Art
It is known to provide a vacuum packaging apparatus for use in evacuating the air in an open-ended package and sealing the evacuated package. A typical apparatus of this type presents a chamber sized only for receipt of the open end of the package with the remainder of the package disposed outside of the chamber, and a vacuum pump communicating with the chamber for evacuating the chamber and the package through the open end. Typically, the sealing mechanism includes a heating element disposed outside the vacuum chamber and extending along the front of the base beyond the ends of the vacuum chamber. The heating element is fixed to the cover so that when the cover is lowered onto the base, the heating element is pressed against a portion of the package external of the chamber. Upon evacuation of the package, current is delivered to the heating element, melting the package material to seal the package closed.
Several problems arise during use of a conventional vacuum packaging apparatus of this type. For example, during heavy use of the apparatus, e.g. in a commercial setting, where a number of packages are evacuated and sealed one after another, there is a tendency for the heating element to retain heat for a period of time well beyond the end of a packaging operation. As a result, when a subsequent package is placed in the apparatus for evacuation and sealing, the heating element presses against the package and prematurely seals it before the air in the package can be evacuated. Further, as heat is retained by the heating element, the temperature of the element increases with each sealing operation, and there is a tendency for the element to melt completely through the package material, resulting in a defective seal.
Another drawback to the use of a conventional vacuum packaging apparatus of the type described is that larger packages must be used with the apparatus than is necessary or desirable. For example, in addition to having to provide an empty area at the open end of each package for receipt in the vacuum chamber, an additional area must also be left empty in the region of the heating element so that the element can press the two opposing sides of the package together for sealing. Thus, a substantial region of each package must be left empty in order to accommodate use of the apparatus in evacuating and sealing the package.